1. Field of the Invention
The present invention relates to a sheet feeding device mounted on an image forming apparatus such as a laser beam printer and a copying machine.
2. Description of the Related Art
An image forming apparatus is provided with a sheet feeding device for storing and feeding sheets. The sheet feeding device includes a sheet feeding cassette serving as a sheet storing device, a sheet feeding roller for feeding the sheets stored in the sheet feeding cassette, and a separation unit for separating the sheets to be fed by the sheet feeding roller one by one. An image is formed on the sheet fed by the sheet feeding device in an image forming unit provided in the image forming apparatus. The sheet feeding cassette includes a lifting plate that is attached rotatably to a cassette case, and the lifting plate is lifted up by a pressing member, so that the sheets supported by the lifting plate are pressed against the sheet feeding roller. The sheet feeding roller rotates to sequentially feed the sheets one by one from the sheet on the top.
Since the lifting plate is not fixed though it is attached to the cassette case, the lifting plate is caused to tumble due to vibration during transport such as shipping from a factory to break other parts of the sheet feeding cassette or is deformed in some cases. Therefore, it is necessary to fix the lifting plate and prevent the lifting plate from tumbling during transport. As a means for fixing the lifting plate, in general, the lifting plate has heretofore been fixed by using a packaging material such as foamed polystyrene and a cardboard.
Japanese Patent Application Laid-Open No. 2000-219332 discusses a configuration of fixing a lifting plate to a cassette case by using a dedicated fixing means such as a screw. In this configuration, before an image forming apparatus is put into use, the lifting plate is made rotatable by removing the fixing means.
Further, Japanese Patent Application Laid-Open No. 2007-031064 discusses an image forming apparatus in which a rear end restricting member for restricting a rear end position of a sheet is caused to slide, so that the rear end restricting member and a cassette case sandwich a lifting plate therebetween to fix the lifting plate. In this configuration, the image forming apparatus is used after making the lifting plate movable by slide-moving the rear end restricting member.
However, the packaging material or the fixing member is used only for the transport if the lifting plate is fixed using the fixing member such as the packaging material or the dedicated fixing member. The packaging material or the fixing member is not necessary and is not used after unpacking the apparatus. In short, the packaging material or the fixing member entails an increase in cost.
Further, if the lifting plate is fixed using the rear end restricting member for sheet position restriction, an extra labor of the user is required to move the rear end restricting member after unpacking the apparatus. Also, an elevation mechanism for lifting up the lifting plate may be broken when the image forming apparatus is actuated without moving the rear end restricting member.